Method of making mica rings



Dec. 30, 1947. L, H R Re. 22,954

METHOD OF MAKING M'ICA RINGS Original Filed Oct. 28, 1940 2 Shets-Sheet l Dec. 30, 1947. L, HOWARD Re. 22,954

METHOD OF MAKING MI CA RINGS Original Filed Oct. 28 1940 2 Sheets-Sheet 2 Reissued Dec. 30, 1947 -METHOD OF'MAKING 'MICA RINGS Leonard ,;L. 1 Howard, Valparaiso, Ind., assignor. to Continental-Diamond Fibre Company, Newark, .Del., a corporation-of Delaware OriginalNo. 2377, 590, datedMarch 24,1942, Scrial No. 363,198,- filedlOctber 28, 1940. Applicationfor-reissue filed August 22, 1947,'Serial .lllvClaims.

1 This invention rclates to aimethod of-manufacturing commutator rings and other annular ,or arcuate bodies having afiange'orflanges.

commutator rings, for example, comprise a radial cross-section including a main, substantially cylindrical body .portion having at one edge thereof an internal V-shaped flange one :wing of which is connected to thebody portion at an acute angle. The usual-practice in manufacture of'these :rings is to provide strips substantially equal in length to the circumference ofthe. proposed ring and to notch that edge of the ring which is gtobe subsequently formed into .the internalV-shaped rib-with which the ring is provided. .The material employed in the construction of the ring is usually mica bonded with a suitable bonding agent such as shellac, copal,

manila gum, a natural resin, or asyntheticresin of suitable 'type,,for example, a Glyptal resin. These rings are placed in a moldinsufiicient number'to build up thecommutator to the desired thickness, following. whichthey are. bonded and cured by heatandpressure. This method of manufacture is disadvantageous due to the fact. thatthe sharp .angle between the flange and body of thering-results in such severe deformation of the sheetsxthat.:breakag of th mica. in the sheets results. "Furthermore, such sheets cannot be readily formed to the contours of the mold,

and there is, accordingly .anadditional tendency to breakage due tothe drag of the walls of the mold as the sheets are moved by the internal plunger of the mold into their final position. Furthermore, the notch-ingot the edges of the sheet often results in disposition of the cuts between adjacent teeth overlying one. another in such fashion-that the dielectric strengthofthe assembly is greatly reduced.

The primary purpose of the presentinvention is the provision of a method of manufacturing such rings whereby such Weaknesses are eliminated and the dielectric strength of the ring,-accordingly, increased.

Another object of the inventionis the provision of a method which will enable the rings-to be cheaply and, at the same time, accurately constructed.

,These and other objects I attain by the method various steps of which are illustrated inthe accompanying drawings in which Fig. 1 is a plan view of one of the primary sections employed in the construction of a ring in accordance with my invention;

Fig. 2 is a fragmentary edge elevation of a layout preceding-initial iormation of the section shownin Fig. 1;

Fig. 3 is a fragmentary sectional view illustrating the primary formation of the sections;

Fig. 4 is a front elevation of a formedsection;

Fig. 5 is a fragmentary perspective of a formed section;

Fig. Sis a-perspective viewvof:the section. after forming and trimming thereof;

' Fig. 7 is a plan view of the formed andtrimmed section;

Fig. 8 .is a fragmentary 1 perspective showing the method of laying up the formed sections-in preparation to final molding ofthe ring;

Fig. 9 is-a perspective .view of the mold showin the sections in; position therein prior, to the final molding; and

Fig. 10 is aperspective view ota completed ring.

In accordance with my method-,.primary sections ;l0,.such asthatshownin Fig.1, .are produced froma prepared sheet or platecomposed of mica and asuitable binder, by anylconvenient processsuch,v for example, as by punch pressing. A pluralityof these sheets .is .then laidup :to for-m a slab ll, .sheet mica, unassociated with binder, indicated at. l2 being placed .betweenadjacent faces of, the individual. sections to prevent adherence during the;f0llowing step. of the process. vThis slab .iSEthEn .heatedto slightlysoften the binder and to .prime;the contained mica for the nextstep of the. process,.as I have found that if a mica slab of thistypevis heated and placed in a cold die, there is; suflicient movement (draw) possible; in the I mica plate :or section to .enable propershaping :01" the ..V.-.shaped flange-i8 without tearing such-asresults. in loss of dielectric strength in the section,.it' being understood that theslabs are made of alengthsuch that disruptive strainsarenot set, up in the flange section. The slabs arethen placed. ina suitable cold press 13, ;as sho n-in-Fig, 3,..and formed into rough sections/such asshown at [4. in Figs. 4 and 5.

These rough sections :arethen trimmed tovthe proper shape, asshowmat15in-Figures 6 and 7, the end edges; being preferably made tangential toa, circle:conoentricawith but smaller than-the mean. internal diameter-of the completedring, following which the; individual sect-ions of the slab are separated,, .as shown in-i'Figure 8,;and placed in a i'lnishing mold 15. lngplacingwhe sections in thegmold, the edges of adjacent strips are staggered with relation to one another so that in a three-deep" ring the solid body of at least two sections will be present at any point 3 in the circumference of the completed ring. The assembled sections are then subjected to heat and pressure to effect the final curing thereof.

It will be noted that by following this method there can be accurate control of the disposition of separated portions of the ring which will render it possible to positively avoid any such weaknesses as occur as a result of overlap of notched edge in the normal process. It will also be noted that, by employing the preforming step, the weakness of the completed ring I! at the joinder of the internal V-shaped flange l8 and the side wall 19 is eliminated.

While the foregoing has been directed entirely to the description of a flanged ring, it will, of course, be understood that the invention is equally applicable to the production of any segmental flanged wall as well.

Since the method as described is obviously capable of modification, I do not Wish to be understood as limiting myself to the specific steps hereinbefore set forth except as hereinafter claimed.

1 I claim:

1. The method of manufacturing flanged rings or segments, comprising forming plates consisting of mica and a binder to a size to form a unit segment of the completed article, assembling a plurality of such plates into a slab with interposed sheets of a material preventing adherence of the plates, heating the slab to soften the binder torender said plates formable and thereafter forming the slab to the desired cross-sectional and circumferential shape, separating the individual plates and laying the plates up in a mold in layers in which the joints of the plates of one layer are staggered with relation to those of remaining layers of the ring, and subjecting the assembly thus provided to heat and to pressure to form the completed article.

2. The method of forming flanged rings or segments, comprising forming a plurality of plates each composed of mica and a binder, preforming said plates into a plurality of unit segments by heating said plates to soften the binder to render said plates formable and thereafter forming them to the desired cross-sectional and circumferential shape, said unit segments being thinner than the desired thickness of the completed article, laying up said unit segments in a mold in layers to the desired thickness while staggering the joints of the unit segments of each layer with relation to the joints between unit segments of adjacent layers, and subjecting the assembly to pressure and to heat to unify the structure.

3. The method according to claim 2, wherein the heated plates are preformed to the desired shape by cold-pressing them.

4. The method of forming flanged rings or segments, comprising forming a plurality of unnotched plates each composed of-mica and a binder, preforming said plates into a plurality of unit segments by heating said plates to soften the binder to render said plates formable and thereafter cold-pressing them to the desired crosssectional and. circumferential shape, said unit segments being thinner than the desired thickness of the completed article, laying up said segments in a mold in layers to the desired thickness while staggering the joints of the unit segments of each layer with relation to the joints between unit segments of the remaining layers, and

4 subjecting the assembly to pressure and to heat to unify the structure.

5. The method of manufacturing rings or seg- ,ments having an acutely related flange, compristhe slab to soften the binder to render said platesformable and thereafter lightly pressing the slab to produce the desired flange and side wall portions without curing the binder, separating the individual plates and laying the plates up in a mold in a layered ring in which the joints of the plates of one layer are staggered with relation to those of remaining layers of the article, and subjecting the assembly thus provided to heat and pressure to form the completed article and cure the binder.

6. The method of manufacturing flanged rings or segments having an acutely related flange, comprising forming unnotched plates of a size to form a unit segment consisting of mica and a binder curable by pressure and heat, assembling a plurality of such plates into a slab with interposed sheets of a material preventing adherence of the plates, heating the slab to soften the binder to render said plates formable, lightly cold-pressing the heated slab to produce the desired flange and side wall portions without curing the same to the insoluble infusible state, trimming the resultant product to provide a true unit segment, separating the individual plates and laying the plates up in a mold in layers in which the joints of the plates of one layer are staggered with relation to those of remaining layers, and subjecting the assembly thus provided to heat and pressure to form the completed article and cure the binder.

7. An article of manufacture consisting of mica and a binder of the type described, said article having a flanged arcuate wall including a plurality of layers of integrally united preformed unnotched unit segments, the joints between the segments of each layer being staggered with relation to those of adjacent layers.

8. An article of manufacture consisting of mica and a binder of the type described, said article having a flanged arcuate Wall including a plurality of layers of integrally united preformed unnotched unit segments, the joints between the segments of each layer being staggered With relationto those of the remaining layers.

9. A commutator ring consisting of mica and a binder of the type described, said ring including a plurality of layers of integrally united preformed unnotched unit segments each having a continuous internally disposed V-shaped flange, the joints between the segments of each layer being staggered with relation to those of adjacent layers.

10. A commutator ring consisting of mica and a binder of the type described, said ring including a plurality of layers of integrally united preformed unnotched unit segments each having a continuous internally disposed V-shaped flange, the joints between the segments of each layer being staggered with relation to those of the remaining layers.

LEONARD L. HOWARD. 

